When constructing a structure such as a building over a ground surface, a foundation may be formed to transfer the weight of the structure, and loads applied on the structure, to the ground in a stable manner, as well as to prevent intolerable levels of defects such as subsidence, inclination, movement, deformation, vibration, etc.
The types of a foundation can be divided largely into a direct foundation (or shallow foundation), which may be applied when the ground is capable of sufficiently supporting the loads of a structure, and which may involve directly transferring the loads from the foundation slab to the ground, and a deep foundation, which may be applied when the ground does not provide a sufficient supporting force or when there is a risk of excessive subsidence, and which may involve transferring the loads of the structure to deeper ground levels by using piles, piers, caissons, etc.
Also known in the art is the top-base foundation (also called the “top-pile foundation”), used on a ground that does not provide a sufficient supporting force, where the ground is reinforced with concrete blocks having the shape of a top and filler gravel, and a direct foundation is formed on the reinforced ground without forming support piles.
FIG. 1 illustrates a top-base foundation according to the related art. Looking at a method of forming a top-base foundation according to the related art with reference to FIG. 1, a positioning frame 60 may be formed by welding rebars to form square grids having equal intervals along the lateral and longitudinal directions over the ground that is to be reinforced and form a triangular grid in a corner of each square grid, and top-shaped concrete piles 10b may be arranged in equal intervals along the lateral and longitudinal directions by forcing the top-shaped concrete piles 10b into the ground with the pile portions 54 inserted through the respective triangular grids. Then, connector rebars 64 placed along the lateral and longitudinal directions may be welded to connector rings 56 that are exposed at the upper surfaces of the top-shaped main portions 52, so that all of the top-shaped concrete files 10b may be connected and secured to one another. Then, the spaces between the ground surface and the bottom parts of the top-shaped main portions 52 of the top-shaped concrete files 10b may be filled with gravel while using a vibration device for compacting the gravel, and the gravel remaining on the upper surfaces of the top-shaped main portions 52 may be removed clean to complete the foundation construction using top-shaped concrete files.
Applying a deep foundation according to the related art on a ground that does not provide a sufficient supporting force may entail the problem of increased costs, as piles, piers, etc., have to be placed up to the deeper ground levels.
Also, the top-base foundation described above may involve a complicated process, due to the critical processes of installing the top-shaped concrete blocks, welding the connector rebars, compacting the filler gravel, and the like, and may hence entail increased construction costs.